Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$221.42	10.654%	$245.0101	$245.01	$245.00	$245.00
Purchase #2	$174.78	6.352%	$185.882	$185.88	$185.90	$185.90
Purchase #3	$144.83	5.440%	$152.7088	$152.71	$152.70	$152.70
Purchase #4	$161.27	10.649%	$178.4436	$178.44	$178.45	$178.40
Purchase #5	$79.25	13.435%	$89.8972	$89.90	$89.90	$89.90
Purchase #6	$35.51	7.805%	$38.2816	$38.28	$38.30	$38.30
Purchase #7	$97.69	7.623%	$105.1369	$105.14	$105.15	$105.10
7 purchase totals =	$914.75		$995.3602	$995.36	$995.40	$995.30